This invention relates to the preparation of 2-phenylethyl alcohols. More specifically it relates to the preparation of 2-phenylethyl alcohols from aromatic aldehydes.
It has long been desirable to prepare 2-phenylethyl alcohol in a low cost process. This material is a valuable intermediate in the preparation of fragrances and of styrene, a commercial chemical with widely varying uses. In the past, it has been proposed that 2-phenylethyl alcohol be prepared from benzyl alcohol. For example, the reaction has been described by Wender, I. et al., J. Amer. Chem. Soc., 71 (1949), pages 4160-4161 wherein the use of a cobalt catalyst was described. This early work is summarized by Orchin in Advances in Catalysis, Vol. V (1953), pages 393-414. This auther reports that, at 183.degree. C., a 50-60 percent yield of toluene and a 23-35 percent yield of 2-phenylethyl alcohol is obtained. Other workers have experimented with this reaction, particularly Y. B. Kryukov et al., Neftekhimiya, 1970, 10 (1), at page 83. Here, a vapor phase reaction is described over an iron, alumina, vanadium and potassium catalyst at 430.degree. C. and 50 atmospheres pressure. Unfortunately, in this latter reaction extremely low selectivities to the 2-phenylethyl alcohol were obtained.
Though not related to the formation of 2-phenylethyl alcohol, homologation has been described by a series of patents assigned to Commercial Solvents, including U.S. Pat. Nos. 3,248,432 and 3,285,948, British Patent 951,506, and Belgian Pat. Nos. 618,413 and 625,939. These references are primarily concerned with the homologation of methanol to form ethanol. The catalyst system shown in U.S. Pat. No. 3,285,948 is of particular interest. This patent discloses the use of a cobalt catalyst promoted with a ruthenium or osmium halide and iodine. The patent also discloses the optional use of from 0.1 to 20 percent of water based on the methanol charged in the reaction system. Reaction temperatures indicated are 175.degree. C. to 230.degree. C., preferably from 190.degree. C. to 210.degree. C.
Unfortunately, the foregoing references fail to result in the preparation of high yields of 2-phenylethyl alcohol. The work reported by Orchin forms so little 2-phenylethyl alcohol that such reaction could not be considered of commercial importance.
Sherwin et al., U.S. Pat. No. 4,158,100 teach that 2-phenylethyl alcohol may be prepared from benzyl alcohol by homologation with hydrogen and carbon monoxide in the presence of a cobalt catalyst promoted with ruthenium and iodine compounds, in the presence of water at a temperature from 100.degree. C. to 165.degree. C.
The present invention gives surprisingly higher yields of the desired 2-phenylethyl alcohols than homologation of benzyl alcohols. These surprising yields are the result of the discovery that 2-phenylethyl alcohol can be prepared from aromatic aldehydes. It has been further discovered that the yields are increased by the use of certain solvents.